[R] how to do this "the R way"

Patrick Burns pburns at pburns.seanet.com
Sat Apr 4 10:27:06 CEST 2009


You need a comma (,) not a dot (.) in your
subscripting of the matrix.  If I get the question
correctly, you want:

newTS2 <- perm[100, TS2]


Patrick Burns
patrick at burns-stat.com
+44 (0)20 8525 0696
http://www.burns-stat.com
(home of "The R Inferno" and "A Guide for the Unwilling S User")

onyourmark wrote:
> Hi. 
>  newTS2 =(perm[100.TS2[1]]. perm[100.TS2[2]]. perm[100.TS2[3]]. ... ,
> perm[100.TS2[2000]])
>
> newTS2 is supposed to be a vector of 2000 values.
> The first value is supposed come from a particular element of the matrix
> called 'perm'.
>
> I thought that 
> perm[100.TS2[1]]
> would be valid code in R to refer to that element.
> It is meant to choose the element from 'perm' in the 100th row and in the
> column indicated by
> TS2[1]. In other words, TS2[1] is the first element in the TS2 vector. 
>
> For example, if the first element in the TS2 vector was 5 then I would want
> to choose the (100,5) element from perm to be the first entry in 
> newTS2.
>
> Does this make sense? Thanks.
>
> onyourmark wrote:
>   
>> Hi. I am sure there is a better way in R to do this then using a loop but
>> I
>> am new to it and not sure what to do. I think it might be something about
>> using a function as an argument but not sure.
>>
>> I have a 1 x 2000 vector TS2 which has entries from the set {x: x is in Z
>> and 0<x<8} (where Z is the set of Integers).
>>
>> Then I also have a 5050 x 7 matrix called 'perm' whose entries are also
>> from
>> the set {x: x is in Z and 0<x<8}
>>
>> I want to construct the following transformation of TS2 which will still
>> be
>> a vector of size 1 x 2000 and which I will call 'newTS2' such that:
>>
>> newTS2 =(perm[100.TS2[1]]. perm[100.TS2[2]]. perm[100.TS2[3]]. ... ,
>>     
>
> Perhaps you can explain what the last line is supposed to do? This is 
> invalid R code and also not a known mathematical notation for me ....
>
> Uwe Ligges
>
>
>   
>> perm[100.TS2[2000]])
>>
>> Is there a nice way to do this without a loop?
>>
>> Thank  you.
>>     
>
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